SpringBoot整合EasyExcel的完整过程记录

2024-04-02 19:55

短信预约 -IT技能 免费直播动态提醒

为什么要用EasyExcel

由于apache poi和jxl，excelPOI都有一个严重的问题，就是非常消耗内存，特别处理数据量多时，速度慢并且时有异常发生，所以改用由阿里研发的easyExcel更可靠一些,它的官方建议对于1000行以内的采用原来poi的写法一次读写，但于1000行以上的数据，有用了一行行进行解析的方案，这样避免了内存的溢出。

1.EasyExcel简介

Java领域解析、生成Excel比较有名的框架有Apache poi、jxl等。但他们都存在一个严重的问题就是非常的耗内存。如果你的系统并发量不大的话可能还行，但是一旦并发上来后一定会OOM或者JVM频繁的full gc。
EasyExcel是阿里巴巴开源的一个excel处理框架，以使用简单、节省内存著称。EasyExcel能大大减少占用内存的主要原因是在解析Excel时没有将文件数据一次性全部加载到内存中，而是从磁盘上一行行读取数据，逐个解析。
EasyExcel采用一行一行的解析模式，并将一行的解析结果以观察者的模式通知处理（AnalysisEventListener）

2.使用EasyExcel实现写

2.1 创建实体类

创建与Excel对应的实体类



@Data
public class DemoData {
    //设置excel表头名称，index表示对应的第几列
    @ExcelProperty(value = "学生编号",index = 0)
    private Integer sno;

    @ExcelProperty(value = "学生姓名",index = 1)
    private String sname;
}

ExcelProperty：指定当前字段对应excel中的那一列。可以根据名字或者Index去匹配。当然也可以不写，默认第一个字段就是index=0，以此类推。

2.2 测试写Excel



public class TestWriteExcel {
    public static void main(String[] args) {
        //实现excel写的操作
        //1.设置写入文件夹的地址和excel文件名称
        String fileName = "D:\\write.xlsx";

        //2.调用easyexcel里面方法实现写操作
        //传入：文件存放的路径+对应的实体类class
        EasyExcel.write(fileName, DemoData.class).sheet("学生列表").doWrite(getData());
    }

    //创建方法返回list集合（测试数据）
    private static List<DemoData> getData() {
        List<DemoData> list = new ArrayList<>();
        for (int i = 0; i < 10; i++) {
            DemoData data = new DemoData();
            data.setSno(i);
            data.setSname("lucy" + i);
            list.add(data);
        }
        return list;
    }
}

结果如下

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-R51xa0VB-1638630992973)(SpringBoot项目整合EasyExcel.assets/image-20211203105225367.png)]

3.使用EasyExcel实现读

3.1 创建读取操作的监听器



public class ExcelListener extends AnalysisEventListener<DemoData> {
    
    @Override
    public void invoke(DemoData data, AnalysisContext analysisContext) {
        System.out.println("****" + data);
    }


    
    @Override
    public void invokeHeadMap(Map<Integer, String> headMap, AnalysisContext context) {
        System.out.println("表头："+headMap);
    }

    
    @Override
    public void doAfterAllAnalysed(AnalysisContext analysisContext) {

    }
}

3.2 测试读Excel



public class TestReadExcel {
    public static void main(String[] args) {
        //读取文件的路径
        String fileName = "D:\\write.xlsx";
        //传入三个参数：文件路径+封装的类的class+监听器
        EasyExcel.read(fileName, DemoData.class,new ExcelListener())
            .sheet()
            .doRead();
    }
}

控制台输出如下

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-ugT2UNpq-1638630992975)(SpringBoot项目整合EasyExcel.assets/image-20211203105451947.png)]

4.springboot项目实践EasyExcel

通过在后台管理上传excel文件添加课程分类（一共两级分类）

4.1 pom中引入相关依赖


<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>easyexcel</artifactId>
    <version>3.0.5</version>
</dependency>

4.2 创建数据库表及添加数据

这里创建一个课程表用EasyExcel实现课程的分类


CREATE TABLE `edu_subject` (
  `id` char(19) NOT NULL COMMENT '课程类别ID',
  `title` varchar(10) NOT NULL COMMENT '类别名称',
  `parent_id` char(19) NOT NULL DEFAULT '0' COMMENT '父ID',
  `sort` int(10) unsigned NOT NULL DEFAULT '0' COMMENT '排序字段',
  `gmt_create` datetime NOT NULL COMMENT '创建时间',
  `gmt_modified` datetime NOT NULL COMMENT '更新时间',
  PRIMARY KEY (`id`),
  KEY `idx_parent_id` (`parent_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 ROW_FORMAT=COMPACT COMMENT='课程科目';


INSERT INTO `edu_subject` VALUES ('1178214681118568449','后端开发','0',1,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178214681139539969','Java','1178214681118568449',1,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178214681181483010','前端开发','0',3,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178214681210843137','JavaScript','1178214681181483010',4,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178214681231814658','云计算','0',5,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178214681252786178','Docker','1178214681231814658',5,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178214681294729217','Linux','1178214681231814658',6,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178214681324089345','系统/运维','0',7,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178214681353449473','Linux','1178214681324089345',7,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178214681382809602','Windows','1178214681324089345',8,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178214681399586817','数据库','0',9,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178214681428946945','MySQL','1178214681399586817',9,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178214681454112770','MongoDB','1178214681399586817',10,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178214681483472898','大数据','0',11,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178214681504444418','Hadoop','1178214681483472898',11,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178214681529610242','Spark','1178214681483472898',12,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178214681554776066','人工智能','0',13,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178214681584136193','Python','1178214681554776066',13,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178214681613496321','编程语言','0',14,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178214681626079234','Java','1178214681613496321',14,'2019-09-29 15:47:25','2019-09-29 15:47:25'),('1178585108407984130','Python','1178214681118568449',2,'2019-09-30 16:19:22','2019-09-30 16:19:22'),('1178585108454121473','HTML/CSS','1178214681181483010',3,'2019-09-30 16:19:22','2019-09-30 16:19:22');

4.3 实体类


@Data
public class SubjectData {
    @ExcelProperty(index = 0)
    private String oneSubjectName;
    @ExcelProperty(index = 1)
    private String twoSubjectName;
}



@Data
@EqualsAndHashCode(callSuper = false)
@Accessors(chain = true)
@ApiModel(value="EduSubject对象", description="课程科目")
public class EduSubject implements Serializable {

    private static final long serialVersionUID = 1L;

    @ApiModelProperty(value = "课程类别ID")
    @TableId(value = "id", type = IdType.ID_WORKER_STR)
    private String id;

    @ApiModelProperty(value = "类别名称")
    private String title;

    @ApiModelProperty(value = "父ID")
    private String parentId;

    @ApiModelProperty(value = "排序字段")
    private Integer sort;

    @ApiModelProperty(value = "创建时间")
    @TableField(fill = FieldFill.INSERT)
    private Date gmtCreate;

    @ApiModelProperty(value = "更新时间")
    @TableField(fill = FieldFill.INSERT_UPDATE)
    private Date gmtModified;
}

4.4 Controller层


@Autowired
private EduSubjectService subjectService;

//添加课程分类
//获取前端上传过来的excel文件，把文件内容读取出来保存到数据库
@PostMapping("addSubject")
public R addSubject(MultipartFile file){

    subjectService.saveSubject(file,subjectService);
    return R.ok();
}

4.5 Service层


//添加课程分类
@Override
public void saveSubject(MultipartFile file, EduSubjectService subjectService) {
    try {
        //得到文件的输入流
        InputStream in = file.getInputStream();
        //调用方法进行读取
        EasyExcel.read(in, SubjectData.class, new SubjectExcelListener(subjectService)).sheet().doRead();

    } catch (Exception e) {
        e.printStackTrace();
    }

}

4.6 创建监听器（核心部分）



@Component
public class SubjectExcelListener extends AnalysisEventListener<SubjectData> {

    public EduSubjectService subjectService;

    public SubjectExcelListener(EduSubjectService subjectService) {
        this.subjectService = subjectService;
    }

    public SubjectExcelListener() {
    }

    //读取excel内容，一行一行读取
    @Override
    public void invoke(SubjectData subjectData, AnalysisContext analysisContext) {
        if (subjectData == null) {
            throw new GuliException(20001, "文件数据为空");
        }
        //一行一行读取，第一个值为一级分类，第二个值为二级分类

        //先判断一级分类是否重复
        EduSubject existOneSubject = this.existOneSubject(subjectData.getOneSubjectName(), subjectService);
        //没有相同的一级分类
        if(existOneSubject==null){
            existOneSubject=new EduSubject();
            existOneSubject.setParentId("0");
            existOneSubject.setTitle(subjectData.getOneSubjectName());
            subjectService.save(existOneSubject);
        }

        //获取一级分类的id值
        String pid=existOneSubject.getId();

        //判断二级分类是否重复
        EduSubject existTwoSubject = this.existTwoSubject(subjectData.getTwoSubjectName(), subjectService, pid);
        if(existTwoSubject==null){
            existTwoSubject=new EduSubject();
            existTwoSubject.setParentId(pid);
            existTwoSubject.setTitle(subjectData.getTwoSubjectName());
            subjectService.save(existTwoSubject);
        }
    }

    //判断一级分类不能重复添加
    private EduSubject existOneSubject(String name, EduSubjectService subjectService) {
        LambdaQueryWrapper<EduSubject> queryWrapper = new LambdaQueryWrapper<>();
        queryWrapper.eq(EduSubject::getTitle, name)
            .eq(EduSubject::getParentId, "0");
        EduSubject oneSubject = subjectService.getOne(queryWrapper);
        return oneSubject;
    }
    //判断二级分类不能重复添加
    private EduSubject existTwoSubject(String name, EduSubjectService subjectService,String pid) {
        LambdaQueryWrapper<EduSubject> queryWrapper = new LambdaQueryWrapper<>();
        queryWrapper.eq(EduSubject::getTitle, name)
            .eq(EduSubject::getParentId, pid);
        EduSubject twoSubject = subjectService.getOne(queryWrapper);
        return twoSubject;
    }
    @Override
    public void doAfterAllAnalysed(AnalysisContext analysisContext) {

    }
}